The present invention relates to an apparatus for controlling the temperature of a cooking location of a cooking unit. More specifically, the present invention refers to a temperature limiter of a type having a temperature sensor including an outer tube and an inner rod accommodated in the outer tube, and a switch base carrying at least one contact actuated by the temperature sensor.
Cooking units or cooktops have typically one or more cooking locations which serve as placement area for cooking utensils and are formed by a plate of ceramic glass and an underlying housing which defines with the plate a heating chamber. Such cooking locations can be heated in a wide variety of ways, e.g. by electric thermal resistors, halogen lights, gas or the like. Regardless of the type of heating element, overheating should be avoided to prevent a destruction of the glass ceramic plate. Typically, temperature limiters are employed to control and limit the temperature of the cooking location. These temperature limiters include a temperature sensor which actuates contacts positioned in the switch base when the detected temperature of the cooking location is excessive, and causes a reduction or stoppage of a gas supply to the cooking location.
When using gas to heat the cooking location, it is necessary to provide within the heating chamber in addition to the temperature limiter a further device to monitor whether ignition of gas has actually occurred within a certain time period after opening the gas supply. If gas is not ignited within a given period, the gas supply must be interrupted. A failed ignition is indicated by respective signaling devices to the user of the cooking location who then has to attempt a renewed ignition for operating the cooking location.
The device for monitoring ignition is conventionally formed by an electrode which projects into the heating chamber at a distance to the burner housing and is electrically insulated from the burner housing in the feedthrough region. Outside the heating chamber, the electrode is connected to the burner housing via a current measuring device.
Ionization of the atmosphere in the heating chamber by a gas flame generates a potential differential between the electrode and the burner housing for producing via the current measuring device a slight compensating current approximately in the range of 5 to 10 .mu.A. When this current can be measured, the ignition can be considered successful, and the gas supply can be maintained. A failure to detect a current, however, means that the ignition attempt was unsuccessful so that the gas supply must be aborted and a respective signal set.
To date, the electrode for this monitoring device is formed as a component that is separate from the temperature limiter. Thus, it is necessary to break through the wall of the burner housing to provide space for the temperature limiter, on the one hand, and the electrode, on the other hand. Moreover, both these distinct units must be separately installed when assembling the cooking location, rendering the construction relative complicated and the overall assembly time-consuming.